The effect of Zinc sulphate intoxication on tissue glycogen content of nine nutritionally important species of fish was observed after 3 hours exposure to concentrations ranging from 5 to 20 ppm. Liver and muscle showed an inverse relationship between the concentration of Zinc and the fall in the glycogen content. However, in brain and kidney a rise in glycogen content was observed upto 10 ppm. of Zinc intoxication. There was a marked fall in glycogen content at 15 and 20 ppm. of Zinc intoxication in brain and kidney tissues. The breakdown process of glycogen was higher in major-carps than in snake-headed and cat-fishes. Major-carps are less resistant to changed environmental conditions (Zinc intoxication) than the other two groups of fishes. The observed physiological changes are briefly discussed in relation to tissue hypoxia and an increase in metabolic products such as lactic acid.